Carbidopa/levodopa gastroretentive drug delivery

ABSTRACT

A gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract comprises internal layer or compartment comprising an active agent and one or more pharmaceutical excipients, of which at least one is a polymer and two membranes forming together an envelope around the inner membrane, each membrane comprising at least one polymeric combination of an enteric polymer which is not soluble in gastric juice, and an hydrophilic swelling polymer, and at least one plasticizer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Applications Nos. 61/046,261, filed on Apr. 18, 2008, and 61/120,051, filed Dec. 4, 2008, and which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention is related to multi-layered, biodegradable gastroretentive drug formulations for the controlled release of active pharmaceutical agents with a narrow absorption window in the upper gastrointestinal tract, that act locally in the gastrointestinal tract, or that possess other rationales for gastric retentive administration. Further, the invention describes multi-layered, biodegradable gastroretentive drug formulations for the immediate release and sustained release of such active agents. The gastroretentive drug formulations of the invention may be administered orally to a mammal for the systemic or local treatment of a pathologic condition or deficiency.

BACKGROUND OF THE INVENTION

Administration of some drugs, such as amino and nucleic acid analogs, peptides peptidomimetic drugs, various antibiotics, various anti-viral drugs, and some others, to a mammal, results in delivery to gastrointestinal tract and absorption of these drugs only in specific regions of the gastrointestinal tract, like the stomach, duodenum and small intestine, such that only drugs delivered to proximity of these regions are absorbed. This phenomenon is frequently referred to as “narrow absorption window” (NAW). Various other drugs' action sites are located in specific regions of the gastrointestinal tract. In addition, various other drugs, such as water-insoluble drugs, possess pharmaceutical rationales for gastric retentive administration. Moreover, the transit time through every region of gastrointestinal tract is a highly variable value.

Despite the advances in sustained release technology for many drugs, controlled release of drugs having a relatively narrow absorption window in the gastrointestinal tract remains a challenge. A need exists to extend the gastric residence time for these drugs, so that the drug is released into the proximity of its site of absorption (or action) for an extended period, or reaches other sites of the GI tract in a uniform manner. Examples of delivery systems capable of increasing the residence time of a drug are floating low-density dosage forms, such as so-called hydrodynamically-balanced delivery systems, effervescent systems comprising gas-generating materials Also other delivery systems, such as high-density dosage forms and bioadhesive or mucoadhesive formulations that slow upper GI transit by adhering to the intestinal mucosa have been attempted (Hwang, S J. et al., Critical Reviews in Therapeutic Drug Carrier Systems, 15 (3): 243-84 (1998); Desai, S. and Bolton, S., Pharmac. Res. 10 (9): 1321-25 (1993); Whitehead, L., et al., European J. Pharm. Sci., 4 (1): S182 (1996); Iannuccelli, V. et al., Intern. J. Pharmac. 174: 55-62 (1998); Jimenez-Castellanos, N R. et al., Drug Develop. Industr. Pharmacy 19: 143 (1993); Moës, A J. Crit. Rev. Ther. Drug Carrier Syst. 10 (2): 143-195 (1993)).

Controlled-release (CR) drug formulations present the advantage of delivering the drug of interest over a prolonged time intervals and eliminating the inconvenience of repetitive daily dosages with concomitant side effects. However, conventional CR drug delivery systems are seldom suitable for drugs with a relatively narrow absorption window in the gastrointestinal tract, since their residence time in or above the absorption window is shorter than the release time span that could be deemed beneficial. Thus, there is a need in the art for controlled-release drug formulations that provide sustained release of drugs having a relatively narrow absorption window in the gastrointestinal tract. Similarly, it is deemed beneficial in certain instances to establish therapeutic blood levels quickly and sustain them over longer periods, the subject known in the art as “the loading dose”, and there is a need in the art for a combined drug formulation comprising an immediate release component and a sustained release component suitable for delivery of narrow-absorption window substances. U.S. Pat. No. 6,685,962 B2, incorporated herein by reference, provides pharmaceutical gastroretentive drug delivery systems for the controlled release of an active agent in the gastrointestinal tract.

The present invention satisfies the need in the art for formulations that provide sustained release or combined immediate release and sustained release of drugs with a narrow absorption window in the gastrointestinal tract, or other rationales for a gastroretentive administration, by providing gastroretentive drug formulations that are also completely biodegradable, and with a relatively high loading capacity.

SUMMARY OF THE INVENTION

Further to these objects, the invention provides biodegradable, multi-layered gastroretentive drug formulations for the sustained release of an active agent in the gastrointestinal tract. In another aspect, the invention provides biodegradable, multi-layered gastroretentive drug formulations for combined immediate release and sustained release of an active agent in the gastrointestinal tract.

In one embodiment, a biodegradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the stomach and gastrointestinal tract of a patient, includes an internal layer containing an active agent and a degradable polymer which is not instantly soluble in gastric fluid. The internal layer includes a first side and an opposing second side. At least one membrane is covering the internal layer. The membrane comprises at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media, the membrane being hydratable in the gastric media. The membrane is directly secured to and covers both sides of the internal layer and has a predetermined length greater than 20 mm in a planar orientation, the membrane and internal layer being arranged in an accordion folded orientation sufficiently compact to be placed within a capsule dissolvable within the stomach of a patient and simulated gastric media. The membrane and internal layer unfold from the accordion folded orientation to a length of at least 20 mm within 30 minutes of being exposed to gastric media. The membrane permits passage of gastric media from the environment to the internal layer and permits passage of the active agent from the internal layer through the membrane to the environment.

In another embodiment, a biodegradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract, includes an internal layer comprising an active agent and a degradable polymer which is not instantly soluble in gastric fluid. A first and second membranes cover the internal layer, the membranes including at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media and the membranes being hydratable. The first and second membranes are having a width and length greater than a width and length of the internal layer. The first and second membranes are being ultrasonically welded or otherwise affixed or attached directly together about the periphery of the first and second membranes. The first membrane is being ultrasonically welded to a first side of the internal layer, the second membrane is being ultrasonically welded to the second side of the internal layer. The ultrasonically welded internal layer and first and second membranes have a predetermined length greater than 20 mm in a planar orientation, the membrane and internal layer being arranged in an accordion folded orientation sufficiently compact to be placed within a capsule dissolvable within the stomach or simulated gastric media. The ultrasonic welds having sufficient mechanical strength and stability to remain intact when being exposed to gastric fluid.

In still another embodiment, a biodegradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract is disclosed, including an internal layer comprising an active agent and a degradable hydrophilic polymer which is not instantly soluble in gastric fluid and a degradable enteric polymer which is substantially insoluble at pH less than 5.5, and optionally a plasticizer. At least one membrane covers the internal layer, the membrane includes at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media, and at least one plasticizer. The membranes swell in the presence of gastric fluid. At least one of the materials in each of the internal layer and membranes are being capable of being ultrasonically welded together. The membrane is directly secured to and covers both sides of the internal layer and has a predetermined length greater than 20 mm in a planar orientation. The membrane and internal layer are being arranged in an accordion folded orientation sufficiently compact to be placed within a capsule dissolvable within the stomach or in simulated gastric media. The membrane permits passage of gastric media from the environment to the internal layer and permits passage of the active agent from the internal layer through the membrane to the environment. The membrane and internal layer unfold from the accordion folded orientation to a length of at least 20 mm within 30 minutes of being exposed to gastric fluid.

In still another embodiment a biodegradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract includes an internal layer comprising an active agent and a degradable hydrophilic polymer which is not instantly soluble in gastric fluid and a degradable enteric polymer which is substantially insoluble at pH less than 5.5, and a plasticizer. First and second membranes cover the internal layer, the membranes include at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media, and at least one plasticizer. The membranes swell in the presence of gastric fluid. At least one of the materials in each of the internal layer and membranes are being capable of being ultrasonically welded together.

The membranes being directly secured to and covering both sides of the internal layer and having a predetermined length greater than 20 mm in a planar orientation, the membranes and internal layer being arranged in an accordion folded orientation sufficiently compact to be placed within a capsule dissolvable within the stomach. The membranes and internal layer unfold from the accordion folded orientation to a length of at least 2.0 mm within 30 minutes of being exposed to gastric fluid. The first and second membranes have a width and length greater than a width and length of the internal layer. The first and second membranes are ultrasonically welded or otherwise affixed or attached directly together about a periphery of the first and second membranes. The first membrane is ultrasonically welded to a first side of the internal layer. The second membrane is ultrasonically welded to the second side of the internal layer. The membrane permits passage of gastric media from the environment to the internal layer and permits passage of the active agent from the internal layer through the membrane to the environment. The ultrasonically welded internal layer and first and second membranes have a predetermined length greater than 20 mm in a planar orientation. The membrane and internal layer being arranged in an accordion folded orientation sufficient to be placed within a capsule dissolvable within the stomach. The ultrasonic welds having sufficient mechanical strength and stability to remain intact when being exposed to gastric fluid.

In one embodiment, the gastroretentive drug formulations are for the sustained release of an active agent in the gastrointestinal tract and comprise: i.) an internal layer or compartment comprising the active agent and one or more pharmaceutical excipients, of which at least one is a polymer; ii.) two membranes forming together an envelope around the inner membrane, each comprising at least one polymeric combination of a polymer which is not soluble in gastric juice, and a hydrophilic swelling polymer, and at least one plasticizer; and iii.) optionally an additional layer covering each outer membrane comprising a powder or a film that prevents adherence of the outer membrane onto itself when folded inside the capsule.

In a different embodiment, the gastroretentive drug formulations are for the immediate release and the sustained release of an active agent in the gastrointestinal tract and comprise: i.) an internal layer or compartment comprising the active agent and a polymer; ii.) two membranes forming together an envelope around the inner membrane, each comprising at least one polymeric combination of a polymer which is not soluble in gastric juice, and a hydrophilic swelling polymer, and at least one plasticizer; and iii.) one or two layers comprising the active agent and a soluble polymer that provides for the immediate release of the active agent and is attached to the outside of one outer membrane or both outer membranes or part of an outer membrane. Optionally an additional layer may be covering each immediate release membrane comprising a powder or a film that prevents adherence of the outer membrane or IR membrane onto itself when folded inside the capsule. In some embodiments, the immediate-release membranes possess surface properties that prevent adherence onto itself when folded inside the capsule.

In preferred embodiments, the gastroretentive drug formulations effectively unfold and retain their mechanical integrity in acidic pH for up to 24 hours and completely biodegrade after 3 hours in simulated intestinal fluid.

In one aspect, the polymer in the internal layer is a degradable polymer which is not instantly soluble in gastric fluid, in another aspect, the polymer is a degradable enteric polymer which is substantially insoluble at pH less than 5.5. The invention also contemplates mixtures of polymers as described above.

In one embodiment the enteric polymer in the internal layer is polymethacrylate copolymer. In different embodiments, the enteric polymer is cellulose acetate phthalate, or hydroxypropylmethyl cellulose phthalate, or hydroxy-propyl methyl cellulose acetate succinate. In a preferred embodiment, the active agent and the polymer are substantially uniformly distributed in the internal layer.

In another embodiment, the polymeric combination of the outer membranes comprises gelatin and hydroxypropyl methyl cellulose acetate succinate as enteric polymer. In one embodiment, the enteric polymer in the outer membranes is polymethacrylate copolymer type A. In a different embodiment, the enteric polymer in the outer membranes is polymethacrylate copolymer type C. In a further embodiment, the plasticizer in the outer membranes is propylene glycol.

In a preferred embodiment, the internal layer or compartment, the outer membranes and the optional additional layers or the immediate release layers are sealed by applying ultrasonic welding.

In an additional embodiment, the internal layer provides at least 50% of the mechanical strength of the whole GRDF when wetted with gastric fluid. In a preferred embodiment, the gastroretentive drug formulation reaches its maximum strength within one hour in simulated gastric fluid. In yet another preferred embodiment, the internal layer has a planar-accordion geometry that unfolds to at least 50% of its original length within 30 minutes in gastric media.

In one aspect, the gastroretentive drug formulation is fully degradable within 3 hours in simulated intestinal fluid. In an additional aspect, the gastroretentive drug formulation provides gastric retention for up to 24 hours under low or medium calorie diet. In yet another aspect, the gastroretentive drug formulation moves in the stomach during gastric retention.

The gastroretentive drug formulations are designed for oral administration and are compacted or folded into a standard size capsule which is easily swallowed. The active ingredient or ingredients is/are incorporated in the gastroretentive drug formulations as dissolved matter in composition of the formulation, powders, grains, spheres, particles, microparticles, nanoparticles, multiparticulates, tablets or microcapsules.

In one aspect, the active agent has a narrow window of absorption in the gastrointestinal tract. The active agent can be a therapeutic nucleic acid sequence, a therapeutic protein or peptide, amino acid analogs, a peptidomimetic drug, a nucleoside analogue, an antibiotic, a therapeutic ion, a vitamin, a bronchodilator, an anti-gout agent, an anti-hypertensive agent, a diuretic agent, an anti-hyperlipidemic agent, an ACE inhibitor, an anti-tumor agent, an histamine (H2) blocker, a bismuth salt or a synthetic prostaglandin. In one aspect, the active agent is levodopa and levodopa/carbidopa mixture. Preferred antibiotic agent is selected from a beta-lactam group, and from fluoroquinolone group.

In another aspect the active agent is a drug for the local treatment in the gastrointestinal tract, such as various drugs for the treatment of local infections, or drugs for the treatment of various gastrointestinal diseases and symptoms, or drugs for the treatment of metabolic disorders, such as obesity, diabetes, hyper-cholesterol, or for the treatment of local cancers or for the treatment of cancer related diseases. In preferred aspects the drugs comprise serotonergic compounds and another enteric neuromodulators, poorly absorbed substances, poorly absorbed antibiotics and compounds, acting in the liver as primary pharmacological site.

The foregoing general description and following brief description of the drawings and the detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Other objects, advantages, and novel features will be readily apparent to those skilled in the art from the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of the GRDF design showing the planar dimensions of the whole GRDF and of the internal layer.

FIGS. 2A and 2B show the placement of a single immediate release layer on top of the outer membrane in a cross section view (A). As shown in (B), the immediate release layer covers the entire surface of the GRDF.

FIG. 3 shows the physical dimensions of the GRDF formulations shown in Example 11.

FIG. 4 shows a GRDF folded inside capsule prior to placing the capsule cap. Visible are the folds and their fold geometry.

FIG. 5 provides results indicating the mechanical properties of GRDFs and films cut into a dog bone shape. The photographs marked 1, 2 and 3 show the stages of mechanical testing of a GRDF after immersion in SGF. The figure in the top right corner shows the results as expressed in a load-to-displacement graph, where the stages of the test correspond to the stages shown in photographs 1, 2 and 3, respectively.

FIGS. 6A and 6B show the design of the anvil (A) and horn (B) of the ultrasound welding machine used for attaching the GRDF layers together.

FIGS. 7A and 7B show a drawing of the ultrasound welding on the GRDF (A). The perimeter line of the internal layer is shown with an arrow and the extent of welding in a cross section of the GRDF is provided (B).

FIG. 8 shows a welded GRDF.

FIG. 9 shows the dissolution profile of a combined immediate release and controlled release carbidopa/levodopa GRDF.

FIGS. 10 and 11 show the measurements from the unfolding of a placebo GRDF device in acetate buffer and SGF.

FIG. 12 shows the mean dose-adjusted Carbidopa concentrations for single dose GRDF CD/LD 75/300 mg gastric retentive, IR+CR; single dose Sinemet® IR 100/25 mg; and single dose Sinemet CR® 25/100 mg, as described in Example 7.

FIG. 13 shows the Levodopa Least-Squares Mean Concentrations in blood samples versus time in subjects treated with GRDF CD/LD 75/300 mg; GRDF CD/LD 50/200 mg; and Sinemet® TR CD/LD 50/200 mg, as described in Example 10.

DETAILED DESCRIPTION OF THE INVENTION Definitions

“Gastroretentive dosage form” as used herein refers to dosage forms with delayed gastric emptying as compared to food (or retention in the stomach beyond the retention of food).

“Simulated gastric fluid” and “Gastric medium”, and “Simulated intestinal fluid” and “Intestinal medium”, as used interchangeably herein refer to media, occurring in stomach and in intestines, correspondingly, or to the solutions that are used to mimic their chemical and/or enzymatic environment in vitro. One such media is described in Example 2.

The term “degradable” as used herein is intended as capable of being chemically and/or physically reduced, dissolved or broken down in the body of a patient and within a relevant time period.

The phrase “polymer which is not instantly soluble in gastric fluid” as used herein means that the polymer will gradually dissolve in the GI tract during its residence therein.

The term “inert” as used herein refers to components in the internal layer or compartment, outer membranes, optional layers and/or the immediate release layers that do not react with the active ingredient or affect its properties under normal conditions, or cause any biological effect upon administration to a subject.

The phrase “prolonged period” as used herein intends a period of delivery that lasts for several hours to about 24 hours, usually above 5 hours, and often between about 5 and 15 hours.

The terms “swellable” and “swelling” mean, with respect to a polymer, that the polymer is capable of imbibing fluid and expanding when in contact with fluid present in the environment of use.

The terms “active agent” and “drug” are used interchangeably herein and refer to an active pharmaceutical ingredient (API), compound, composition of matter or mixture thereof which provides a therapeutic or prophylactic effect.

A “patient” as referenced herein is a human or non-human mammal who may need to receive the gastroretentive drug formulations of the present invention.

“Treating” or “treatment”, are used herein to refer to obtaining a desired pharmacological and physiological effect. The effect may be prophylactic in terms of preventing or partially preventing a disease, symptom or pathological condition and/or may be therapeutic in terms of a partial or complete cure of a disease, condition, symptom or adverse effect attributed to a pathological condition. Thus, “treatment” covers any treatment of a disease in a mammal, particularly a human, and includes: (a) preventing a pathological condition from occurring in an individual which may be predisposed to develop a pathological condition but has not yet been diagnosed as having it, i.e., causing the clinical symptoms of a pathological condition not to develop in a subject that may be predisposed to develop the condition but does not yet experience or display symptoms of the condition; (b) inhibiting, i.e., arresting or reducing the development of the pathological condition or its clinical symptoms; or (c) relieving symptoms associating with the pathological condition.

In the current embodiments, the gastroretentive drug delivery system includes an internal layer and an outer layer. The outer layer is formed from two films which are slightly larger than the internal layer and which are sealed or welded together around their perimeter and completely envelope the internal layer. Along with welding which connects the outer layers together, the outer portion of the internal layer is also welded to the outer layers.

Alternatively, in the current embodiments, the gastroretentive drug delivery system includes an internal layer and an outer layer, whereas the outer layer is formed from two membranes which are equal in size with the internal layer and which are sealed or welded together around their perimeter and the outer portion of the inner layer. Optionally the gastroretentive delivery system comprises an additional layer which is either larger or equal in size to the inner/outer membranes assembly, and envelops the assembly to prevent adhesion of the membranes onto themselves; the said layer can be formed with one or more membranes, ultrasonically welded or otherwise attached or affixed onto the assembly, and can optionally comprise an API. The ultrasonically welded or otherwise attached internal layer and outer layers are folded in an accordion arrangement and placed within a capsule. In some embodiments, the capsules are made from gelatin or hypromelose. The layers are shaped in essentially oval polygonal form such that they maximize the amount of space within the capsule that is filled. Once the gelatin or hypromelose capsule dissolves within the gastric medium, the internal layer and outer layers expand from the accordion folded orientation to a more planar orientation.

The gastroretentive drug formulations of the present invention markedly improve absorption and bioavailability of suitable active agents, and, in particular, ameliorate the absorption and bioavailability of drugs having a narrow window of absorption in the gastrointestinal tract, due to its ability to withstand peristalsis and mechanical contractility of the stomach, and consequently, release the drug in a controlled manner onto its absorption sites and without premature transit into non-absorbing regions of the GI tract. The inventors discovered that the gastroretentive drug formulation provides gastric retention of active agents having a narrow window of absorption for up to 24 hours under low or medium, calorie diet, unlike other formulations in the art, that require high calorie and high fat diet for proper functioning. In addition, administration of these formulations to a mammal can improve the pharmacokinetic and pharmacodynamic properties of active agents having a narrow window of absorption. Since the gastroretentive drug formulations are fully degradable, they provide a means to administer the proper dose of the drug without generating non-degradable residues that would not be eliminated after drug release.

The gastroretentive drug formulations are stable, fully degradable and provide efficient delivery of various drugs in the gastrointestinal tract due to the combination of an internal layer having planar-accordion geometry where all components are fully biodegradable. The combination of swelling outer membrane layers with a substantially non-swelling internal layer having planar accordion geometry causes the internal layer to undergo an unfolding process once the formulation reaches the stomach, thus extending gastric residence time and preventing the dosage form from being evacuated until substantial or complete release.

Sustained-Release Gastroretentive Drug Formulations

In accordance with the first embodiment of the invention, a stable, degradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract is provided. The gastroretentive drug formulation comprises: i.) an internal layer or compartment comprising the active agent, one or more polymers and one or more modifying agents such as plasticizers and/or solubilizers and/or fillers; ii.) two outer membranes, each comprising at least one polymeric combination of hydrophilic polymer and a polymer insoluble in gastric media, and at least one plasticizer; and iii.) optionally an additional layer covering each outer membrane and comprising a powder or a film that prevents adherence of the outer membranes to itself.

In accordance with another embodiment of the invention, degradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent can be combined with one or more immediate release layers covering the outer membranes and comprising the active agent and a polymer and optionally other excipients, known in the art, that provides for the immediate release of the active agent to form degradable, multi-layered gastroretentive drug formulation for combined immediate-release and sustained-release of the active agent. Optionally an additional layer covering each outer membrane and comprising a powder or a film that prevents adherence of the outer membranes to itself is included. Additional disclosure regarding the immediate and controlled release formulations are provided below.

Internal Layer

The internal layer or compartment in the gastroretentive drug formulations comprise the active agent and a polymer substantially uniformly distributed throughout the internal layer. The polymer can be a degradable hydrophilic polymer which is not instantly soluble in gastric fluid, a degradable enteric polymer which is substantially insoluble at pH less than 5.5, a hydrophobic polymer or mixtures thereof. It can further comprise acceptable pharmaceutical additives, such as plasticizers, humectants, fillers and others.

Examples of degradable hydrophilic polymers which are not instantly soluble in gastric fluid suitable for the invention are hydroxypropyl cellulose, hydroxypropylmethyl cellulose, polyvinyl pyrrolidone, polyethylene oxide and methyl cellulose. Preferably, the enteric polymer is a polymethacrylate copolymers, cellulose acetate phthalate, hypromelose acetate succinate or hypromellose phthalate. These polymers are combined with active agent, such as Levodopa and/or Carbidopa. Exemplary ranges for active agents and polymers are provided the table below.

Range In Inner Component Layer Carbidopa 5-17% Levodopa 40-65%  Eudragit L100 10-35%  Poloxamer 407 7-19% PEG 400 4-14%

Preferably, the internal layer has planar accordion geometry. This feature, together with the presence of polymers as described above in the internal layer or compartment provides the internal layer with substantial mechanical strength. Preferably, the internal layer has a mechanical strength with Young's modulus of from about 0.5 to 15 Kgf/mm². Preferably, the range could be from about 3.0 to about 10.0 Kgf/mm² or from about 3.0 to about 6.0 Kgf/mm². The stress may range from about 0.03 to about 0.6 Kgf/mm² after 1 hour in simulated gastric fluid, such that the gastroretentive drug formulation reaches its maximum strength within one hour in simulated gastric fluid. Alternatively the range for stress may be from about 0.05 to about 0.4 Kgf/mm or about 0.1 to about 0.4 Kgf/mm.

The components of the internal layer may be altered based on the characteristics of the active ingredients being delivered. For example, some ingredients may be more soluble in certain polymers than others and may require a reformulation of the internal layer. In some instances, the active ingredient may require a formulation of the internal layer that does not allow effective welding between the outer and internal layer. In such situations, the internal layer may be composed of the two or more portions, where each portion has definite function. In one instance, the central region (welding free) can be formulated as separate film to hold the active ingredient and be placed into the central portion and over the inner film comprising as additional portion that will support this central portion. This additional portion can then be welded to the outer layer. In another instance, whereas the internal layer cannot be formulated to develop the necessary mechanical strength in the gastric medium, at least one additional layer, optionally comprising no drug, could be used as a scaffold, whereupon the formulated drug reservoir film could be laid and welded or otherwise attached or affixed, onto one or both sides of said backbone, and the assembly could be welded to the outer membranes and other components of the delivery system.

Outer Membranes

Each of the outer membranes in the gastroretentive drug formulations comprises at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media, and at least one plasticizer.

Examples of suitable ingredients for the invention include gelatin, hydroxypropylcellulose, hydroxypropyl methycellulose, pectin, polyethylene oxide, starch, and zein. Preferably, the hydrophilic polymer is gelatin. The amount of gelatin in each of the outer membranes is between about 20 and about 45% of the total outer membrane composition, and preferably between about 25 and about 35% of the total outer membrane composition.

Examples of enteric polymers that can be used in the outer membranes include hypromellose phthalate, hypromellose acetate succinate and polymethacrylate co-polymers. Preferably, the enteric polymer is polymethacrylate copolymer type A or polymethacrylate copolymer type C.

Plasticizers suitable tor the invention include various polyethylene glycols, glycerin, triethylcitrate. Preferably, the plasiticizer is propylene glycol.

The outer membranes swell in the presence of gastric fluid and are fully degradable within two hours in simulated intestinal fluid. The combination of swelling outer membrane layers with a non-swelling internal layer having planar accordion geometry causes the internal layer to undergo an unfolding process once the formulation reaches the stomach, thus extending gastric residence time and preventing the drug-containing dosage form from being evacuated until complete release. In one embodiment the internal layer has a swelling rate less than the swelling rate of the membrane.

The membrane permits passage of gastric medium from the environment to the internal layer and permits passage of the active agent from the internal layer through the membrane to the environment.

In some instances the kinetics of such transport can be unacceptably low. Therefore in some embodiments the outer membranes can be perforated with one or more orifices to facilitate the mass transfer processes through the membrane. In preferred embodiments the orifices are uniformly distributed over the area hereabout the formulated drug layer.

In a preferred embodiment, the outer layer does not contain any active ingredient. In other embodiments, the outer layer comprises one or more active ingredients.

Optional Additional Layer

The gastroretentive drug formulations of the invention may further comprise an optional additional layer covering each outer membrane and comprising a powder or a film. In some instances it may be found that the outer layers stick together in the capsule and do not unfold properly upon dissolving of the capsule. In such situations, this optional layer prevents adherence of the outer membranes to themselves and allows for the proper opening of the GRDF. In preferred embodiments, the optional layer comprises at least one powder, and optionally at least one polymer. In other embodiments the preferred polymers are rapidly-dissolving film formers, which can be selected from but not limited to soluble cellulose derivatives, i.e. methyl cellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, hypromelose; various grades of povidone; polyvinyl alcohol and its derivatives, i.e. Kollicoat IR; soluble gums and others. The films may further comprise surface-active agents, plasticizers and humectants.

The Immediate Release Layers

The invention further contemplates gastroretentive drug formulations for combined immediate-release and controlled release of an active agent in the gastrointestinal tract. These formulations comprise an internal layer or compartment and at least two outer membranes as described above, and additionally comprise one or more immediate release layers covering the outer membranes and comprising the active agent and a soluble polymer that provides for the immediate release of the active agent. Examples of soluble polymers that can be used in the immediate release which can be selected from soluble cellulose derivatives, i.e. methyl cellulose, hydroxypropvl cellulose, hydroxyethyl cellulose, hypromelose; various grades of povidone; polyvinyl alcohol and its derivatives, i.e. Kollicoat IR; soluble gums and others. The films may further comprise surface-active agents, plasticizers and humectants, such as PEGs, different grades of polysorbates and sodium lauryl sulfate, for example.

The relative amounts of the polymers may be adjusted based on the solubility on the active ingredient.

While the internal layer and outer layer are generally welded together, the immediate release layer will not generally require such a strong connection with the rest of the GRDF device. Rather the immediate release formulation will quickly dissolve in order to deliver the drug of interest. The immediate release layer may be affixed to the outside of the GRDF using a compatible solvent, ultrasonic welding, or other means.

The ability to add an additional immediate release layer is particularly helpful in the development of GRDFs. By combining the immediate and controlled release nature of the current invention, one can alter the drug release profile for the drug of interest. Consequently, patients may receive both an immediate bolus of the drug as well as a prolonged delivery of the active agent with the purpose of establishing therapeutic levels of the drug quickly and maintaining these levels for prolonged period of time, up to 24 hour.

Of further note is the ability to deliver multiple drugs in the current GRDF. The current embodiments are not limited to the delivery of a single active pharmaceutical agent. Rather, multiple drugs may be formulated and delivered simultaneously. By combining the immediate and controlled release layers, multiple drugs may be simultaneously delivered with specific profiles. For example, a combined release formulation for levodopa/carbidopa is provided in the Examples.

All components of the internal layer or compartment, the outer membranes, the optional layers and/or the immediate release layers are pharmaceutically acceptable and inert.

As an additional method of delivering the immediate release of the drug, a coating may be applied to the capsule comprising the drug. Upon entry into the stomach, the coating will immediately allow release of the drug and enhance the release profile of the drug. Methods for applying coating to a capsule are well known to those of skill in the art.

Ultrasonic Welding

The internal layer or compartment, the outer membranes, the optional layers and/or the immediate release layers may be attached to each other by many means. Preferably, they are sealed by applying ultrasonic welding. One example of a device suitable for these purposes is the Dynamic 745 ultrasonic welder from Rinco Ultrasonics, but other devices may be employed. The welding effectively seals the internal layer within the outer layer by welding the outer layers together and also welding the perimeter of the internal layer to the outer layer. It can also efficiently attach the layers to one another without sealing a whole envelope, meaning that there is no need for same-material welding, should the formulations be compatible.

Different patterns and times may be used for the welding based on the needs of those skilled in the art. Although the periphery of the layers can be welded together, the current embodiments do not weld the central portion of the GRDF device so as to minimize any heating or effects on the majority of the internal layer which holds the active pharmaceutical agent for controlled release. In some situations it may be necessary to weld more of the internal layer based on the composition of the GRDF.

The GRDF Capabilities

The gastroretentive drug formulations are designed for oral administration and are compacted or folded into a standard size capsule which is easily swallowed. The active ingredient or ingredients is/are incorporated in the accordion pill as powders, grains, spheres, particles, microparticles, nanoparticles, multiparticulates, solid solutions, tablets or microcapsules. Active agents that may be delivered with the gastroretentive drug formulations include active agents which act on the peripheral nerves, adrenergic receptors, cholinergic receptors, the skeletal muscles, the cardiovascular system, smooth muscles, the blood circulatory system, synoptic sites, neuroeffector junctional sites, endocrine and hormone systems, the immunological system, the reproductive system, the skeletal system, the digestion system, the histamine system and the central nervous system. Especially preferred are active agents used in the treatment of gastrointestinal diseases, including, but not limited to, duodenal ulcers, gastric ulcers, Zollinger-Ellison syndrome, gastroesophageal reflux disease, erosive esophagitis, gastritis, gastric carcinoma and spasticity. Other indications such as cancer, infections, and metabolic disorders are also envisioned in addition to other conditions known by those of skill in the art which may be addressed through gastroretentive device delivery.

Suitable active agents include, for example, proteins, enzymes, enzyme inhibitors, hormones, polynucleotides, nucleoproteins, polysaccharides, glycoproteins, lipoproteins, peptides, polypeptides, steroids, hypnotics and sedatives, psychic energizers, tranquilizers, anticonvulsants, antidepressants, muscle relaxants, antiparkinson agents, analgesics, immunosuppressants, anti-inflammatories, antihistamines, local anesthetics, muscle contractants, antimicrobials, antimalarials, antivirals, antibiotics, bronchodilators, anti-gout agents, antiobesity agents, antidiabetic agents, anti-hyper-cholesterol agents, hormonal agents including contraceptives, sympathomimetics, anti-hypertensive agents, diuretics, lipid regulating agents, ACE inhibitors, bismuth salts, synthetic prostaglandins, antiandrogenic agents, antiparasitics, neoplastics, antineoplastics, antihyperglycemics, hypoglycemics, nutritional agents and supplements, growth supplements, fats, ophthalmics, antienteritis agents, electrolytes and diagnostic agents.

Preferably, the active agent has a narrow window of absorption in the gastrointestinal tract. Antiviral, antifungal and antibiotic agents, including sulfonamides, quinolones, penicillins, cephalosporins, aminoglycosides, and tetracyclines, are representative classes of active agents that have a narrow window of absorption in the gastrointestinal tract. Specific examples of drugs include, but are not limited to, cimetidine, ranitidine, famotidine, nizatidine, zolentine, metronidazole, imidazole, amoxicillin, clarithromycin, minocycline, tetracycline, somatostatin analogues, including levodopa and carbidopa.

In addition, active agent that act locally are, for example, drugs for the treatment of local infections, or drugs for the treatment of various gastrointestinal diseases and symptoms, or dings for the treatment of metabolic disorders, for the treatment of local cancers or for the treatment of cancer related diseases. More specifically, the agents relevant in this aspect are these that have to be administered in the inflamed bowel, as occurs during inflammatory bowel diseases, such as metronidazole, vancomycin, budesonide and others, whose efficacy is impaired by unusually rapid emptying of the inflamed tissue. These materials can be poorly absorbed systemically, such as vancomycin, or could be incorporated into a targeted delivery system, such as for budesonide.

Other drugs that may be formulated according to the invention include drugs for the treatment of Parkinson's Disease. Parkinson's Disease (PD), one of the most common neurodegenerative diseases of the elderly, is a slowly progressive clinical syndrome characterized by resting tremor, slowness of movement, muscular rigidity, and gait instability. PD may also be accompanied by difficulty in swallowing, loss of olfactory sense, difficulty in speech, depression and dementia. The pathogenesis of PD involves degeneration of dopaminergic neurons in the substantia nigra pars compacta and a consequent depletion of the neurotransmitter dopamine in the basal ganglia. Since dopamine cannot cross the blood-brain barrier, Levodopa (LD) (which is enzymatically decarboxylated by the enzyme L-amino dopa decarboxylase in the CNS to dopamine), is used therapeutically to replenish the brain's diminished dopamine reservoir. LD is considered the most effective therapeutic drug for the treatment of Parkinson's disease. Decarboxylation reaction can also occur at some rate peripherally, even before levodopa reaches the brain. Therefore Levodopa is generally co-administered with an effective L-amino dopa decarboxylase inhibitor such as Carbidopa. The inhibition of Levodopa decarboxylation in the periphery reduces peripheral dopamine formation and decreases the side effects attributed to dopamine (i.e. orthostatic hypotension, nausea and vomiting), while simultaneously increasing the bioavailability of Levodopa to the CNS. Carbidopa/Levodopa is commercially available as a combination products, both as immediate-release (e.g. Sinemet®, Merck & Co., Inc.) or controlled-release (e.g. Sinemet-CR®, Merck & Co., Inc.) tablets.

The plasma half-life of LD is about 50 minutes, without Carbidopa (CD). When CD and LD are administered together, the half-life of LD is increased to about 1.5 hours. At steady state, the bioavailability of LD from Sinemet® tablets is approximately 99% relative to the concomitant administration of Carbidopa and LD.

Although LD is the most effective treatment for Parkinson's disease (PD), there are problems with its long term use. Early PD patients fair well with LD with a sustained response to each LD dose. Over time, however, the duration of the response after each dose declines, resulting in “wearing off”, where the medication does not work until the next dose reaches therapeutic levels. As the disease progresses the patient suffers from longer OFF periods when the LD is not working. In addition, a disabling side effect of LD treatment is the occurrence of dyskinesias, usually as a peak dose effect. Both of these phenomena, wearing off and dyskinesias, are believed to be caused by the pulsatile stimulation of striatal dopamine receptors and the large difference between peak to trough levels of dopamine. It is beneficial, therefore, to provide continuous, rather then pulsatile, dopaminergic stimulation by either increasing the frequency of dosing or by treatment with a controlled release product. The current available controlled release LD treatment, Sinemet CR®, has shown decreased bioavailability and efficacy, since LD is absorbed mainly in the upper intestines and a slow release product that has passed the area of absorption will not be effective.

The GRDF formulations of the invention maintain controlled release of LD, that is retained at or above the area of absorption, the upper intestines, with minimal peak/trough variations, and thus provide the most beneficial treatment in terms of efficacy and safety profiles.

The gastroretentive dosage forms of this invention can conveniently release active agents in a sustained profile or in a combined immediate and sustained profile over a prolonged period, while maintaining high drug bioavailability for an extended period of time.

The detailed description of the present invention is further illustrated by the following examples, which are illustrative only and are not to be construed as limiting the scope of the invention. Variations and equivalents of these examples will be apparent to those skilled in the art in light of the present disclosure, the drawings and the claims herein.

Gastric Retention Under Low and Medium Calorie Diet

The gastroretentive drug formulations maintain their physical integrity over a prolonged period of time, such that the active agent is retained in the stomach for up to 24 hours under low or medium calorie diet. The use of a low and medium calorie diet is advantageous because it follows normal dietary habits of the patients and does not demand an excessive meal with each instance of dosing of the GRDF. Although the GRDF may be retained in the stomach for extended periods of time all of the GRDF components are degradable and undergo complete degradation once they reach the intestine.

The invention is further represented by the following examples. The examples are representative only and are not intended to limit the invention to the particular embodiments described therein.

EXAMPLES Example 1 Ultrasonic Welding of GRDF

In order to weld the layers of the GRDF, the Dynamic 745 ultrasonic welder from Rinco Ultrasonics was used with the following parameters:

Parameters of ultrasonic welding Trigger 275 N Rise of force Trigger 380 N/s Melting time 650 ms Rise of force Trigger 600 N/s Amplitude 9 Solidification force 600 N Holding time 600 ms

FIGS. 6A, 6B, 7A and 7B show the design of the anvil and horn of the ultrasonic welding machine used for attaching the GRDF layers together. In addition, a cross sectional view of the extent of the welded area is provided. FIG. 8 shows an enlarged photograph of a portion of a GRDF with the ultrasonic welding of the outer layers to each other forming an envelope around the internal layer. The welding between the peripheral portion of the internal layer with the outer layer is also visible.

Example 2 Unfolding of GRDF

The following data show that the GRDF of the current invention unfold within a short period of time and would not be quickly passed through the stomach before deployment and release of the active ingredients. The below experiments were conducted with a placebo GRDFs first loaded into capsules and then placed in either SGF pH 1.2 or acetate buffer (USF) pH 4.1 in a USP Apparatus 2, 50 rpm. GRDFs were visually inspected after 15 minutes. In addition, the lengths of the accordion laminates along its longest dimension were measured after 30, 60 and 120 minutes in the medium. Completely flat devices have a length of 45 mm. See FIGS. 10 and 11 for the results. The devices are unfolded by 30 minutes. Visual inspection at 15 minutes indicated that the pills were dissolved and the devices had opened to about the same size as seen at 30 minutes.

Example 3 Mechanical Properties of GRDF

The mechanical properties of the GRDFs and their films wets tested. See FIG. 5 for results. Intact GRDFs, as well as specimens which were cut into a dog bone shape were tested in order to determine their mechanical properties. Values for the strain, load, stress, and Young's modulus are provided.

Example 4 Degradabiiity of GRDF

The following results show the complete biodegradability of the GRDF of the current invention once it is passed into an environment similar to the intestinal tract. Four GRDF devices were placed in simulated intestinal fluid (USP SIF) and monitored every hour for three hours. The devices were not first loaded in a pill, but were placed directly into SIF. After three hours the devices dissolved.

Example 5 Carbidopa-Levodopa GRDF Formulation

A GRDF was manufactured using the following components for the internal layer, outer layers, and an immediate release layer.

Amount/GRDF (mg) Internal Outer (sum of Immediate Component layer two films) Release Layer Total Carbidopa 45.0 30.0 75.0 Levodopa 200.0 100.0 300.0 Eudragit S100 53.2 53.2 Eudragit L100 100.0 26.6 126.6 Eudragit L100-55 26.6 26.6 Fish Gelatin 106.5 106.5 Propylene glycol 106.5 106.5 KOH 6.7 6.7 Poloxamer 407 65.0 65.0 PEG 400 40.0 8.3 48.3 Methylcellulose 4.7 4.7 Povidone 90 18.4 18.4 Total 450 326.1 161.4 937.5

Example 6 Cartoidopa-Levodopa GRDF Release Profiles

In order to illustrate the ability of the GRDF to provide both immediate release and controlled release of active ingredients, the release profile for the above (Example 5) Carbidopa/Levodopa GRDF was determined. Carbidopa and Levodopa are present in total amounts of 75 and 300 mg, respectively. Specifically, there are 30 mg Carbidopa in the immediate release layer and 45 mg in the internal layer which are provided to the patient as a controlled release. For Levodopa, 100 mg are in the immediate release layer and 200 mg in the internal layer.

Experiments were conducted in an acetate buffer (LISP) pH 4.1 in a USP Apparatus 2, 50 rpm. As shown in FIG. 9, immediate release for both drugs occurred within 1 hour and extended release was seen for 8 hours.

These experiments illustrate the ability to effectively deliver a single or multiple drugs at the same time using the current GRDF. If delivered simultaneously, the drugs may be concentrated in the immediate release and controlled release layers to provide the desired profiles and release characteristics in one system.

Example 7 Carbidopa/Levodopa GRDF Pharmacokinetic Profiles Compared to Immediate Release Sinemet® and Controlled Release Sinemet CR® Pharmacokinetic Profiles in Healthy Subjects The Study

A three-way crossover study was performed in healthy subjects to assess the pharmacokinetics of two single GRDF Levodopa/Carbidopa (LD/CD) dose formulations. A single dose of GRDF LD/CD containing Levodopa 300 mg and Carbidopa 75 mg (formulation in Example 5) administered to healthy male subjects after a light meal were compared with Sinemet® containing Levodopa 100 mg and Carbidopa 25 mg and Sinemet CR® containing Levodopa 200 mg and Carbidopa 50 mg.

Pharmacokinetics of Levodopa

The plasma half-life of Levodopa is about 50 minutes, without Carbidopa. When Carbidopa and Levodopa are administered together, the half-life of Levodopa is increased to about 1.5 hours. At steady state, the bioavailability of Carbidopa from Sinemet® tablets is approximately 99% relative to the concomitant administration of Carbidopa and Levodopa.

Carbidopa inhibits decarboxylation of peripheral Levodopa. It does not cross the blood-brain barrier and does not affect the metabolism of Levodopa within the central nervous system.

Carbidopa reduces the amount of Levodopa required to produce a given response by about 75 percent and, when administered with Levodopa, increases both plasma levels and the plasma half-life of Levodopa, and decreases plasma and urinary dopamine and homovanillic acid.

In clinical pharmacologic studies, simultaneous administration of Carbidopa and Levodopa produced greater urinary excretion of Levodopa in proportion to the excretion of dopamine than administration of the two drugs at separate times.

Patients treated with Levodopa therapy for Parkinson's Disease may develop motor fluctuations characterized by end-of-dose failure, peak dose dyskinesia, and akinesia. The advanced form of motor fluctuations (‘on-off’ phenomenon) is characterized by unpredictable swings from mobility to immobility. Although the causes of the motor fluctuations are not completely understood, in some patients they may be attenuated by treatment regimens that produce steady plasma levels of Levodopa.

A current formulation of Levodopa/Carbidopa (Sinemet CR®) provides controlled-release of ingredients over a 4- to 6-hour period. However, the sustained-release product of this combination is less systemically bio available (70 to 75%) than the immediate-release product (99%), and may require increased daily doses to achieve the same level of symptomatic relief. Typical starting doses of LD/CD are Levodopa 100 mg and Carbidopa 25 mg 3 or 4 times a day for a total of 300-400 mg Levodopa daily.

For the purpose of this study, the GRDF CD/LD 75/300 mg was planned for a 600 mg total daily dose of Levodopa.

Since gastric retention can be achieved by eating a high fat, high calorie meal (food retention), true gastric retention was assessed in healthy subjects that were administered a low calorie breakfast.

The Products A. Reference Product

Product Sinemet ® Dose Administered 25/100 (1 tablet) Active Ingredient Carbidopa/Levodopa, immediate release Dosage Form Tablet Strength 100 mg/25 mg Manufacturer MERCK & CO., INC

B. Reference Product

Product Sinemet CR ® Dose Administered 50/200 (1 tablet) Active Ingredient Carbidopa/Levodopa, controlled release Dosage Form Tablet Strength 25/100 mg Manufacturer MERCK & CO., INC

C. Reference Product

Product GRDF CD/LD Dose Administered 75/300 mg Active Ingredient Carbidopa/Levodopa, controlled release Dosage Form capsule Strength 75/300 mg

The Treatment

The single-center, open-label single-dose, three way crossover, pharmacokinetic study was performed in 24 healthy male subjects between 18 and 55 years of age. Adult healthy subjects participated in 3 study days with at least 1 week washout period between days.

All oral formulations were swallowed whole with 240 ml water alter a light breakfast. Standardized meals were given to all subjects throughout the study days.

Venous blood samples was drawn before dosing and then at frequent intervals to match the pharmacokinetic behavior of the drug. Levodopa plasma levels were analyzed.

The results of the study are shown in the Tables below and in FIG. 12:

Levodopa Results

Sinemet 90% 90% GRDF IR Ra- CV CI CI Signif- Lsmean Lsmean tio % Lo Hi icant LnAUC 5164 1218 4.238 11.58 4.008 4.482 ** LnCmax 1400 624 2.243 20.42 2.034 2.474 ** LnMRT 4.45 2.69 1.656 16.12 1.533 1.790 ** LnAUC_DA 5164 3655 1.413 1.336 1.494 ** LnCmax_DA 1400 1873 0.748 0.678 0.825 ** Tmax 2.65 1.40 1.896 ** Sinemet 90% 90% GRDF CR Ra- CV CI CI Signif- Lsmean Lsmean tio % Lo Hi icant LnAUC 5164 3104 1.664 11.58 1.573 1.761 ** LnCmax 1400 1043 1.343 20.42 1.217 1.481 ** LnMRT 4.45 3.54 1.259 16.12 1.165 1.360 ** LnAUC_DA 5164 4655 1.109 1.049 1.173 ** LnCmax_DA 1400 1565 0.895 0.812 0.987 ** Tmax 2.65 2.17 1.221 ** 90% 90% CR IR Ra- CV CI CI Signif- Lsmean Lsmean tio % Lo Hi icant LnAUC 3104 1218 2.547 11.58 2.409 2.694 ** LnCmax 1043 624 1.671 20.42 1.515 1.843 ** LnMRT 3.54 2.69 1.316 16.12 1.218 1.422 ** LnAUC_DA 4655 3655 1.274 1.204 1.347 ** LnCmax_DA 1565 1873 0.836 0.758 0.922 ** Tmax 2.17 1.40 1.552 ** For log-transformed data (Ln) the LSmeans are geometric mean ratios are geometric mean ratios. AUC = AUC 0-t MRT = Mean Residence Time (hours) _DA = Indicates Parameter Was Dose-Adjusted to 300 mg CV % = Estimated Within-Subject Coefficient of Variation ** = p < 0.05, blank entry indicates p > 0.05 (adjusted for multiple pairwise comparisons)

The results show that the GRDF LD/CD, compared to the reference products, extended retention time in the stomach and controlled release of the active ingredients over a 5-hour period. GRDF LD/CD provided prolonged release of the active ingredients at a site above their absorption window and improved bioavailability with fewer variations in plasma levels, thus providing steady plasma levels of Levodopa and Carbodopa.

It is known that patients treated with Levodopa therapy for Parkinson's Disease may develop motor fluctuations characterized by end-of-dose failure, peak dose dyskinesia, and akinesia. These symptoms may be attenuated by treatment regimens that produce steady plasma levels of Levodopa. By providing a quick rise, yet steady level of Levodopa and Carbodopa, the GRDF LD/CD satisfy the need for a combination of immediate release and controlled release mechanism of LD/CD that provide steady plasma levels of Levodopa and Carbodopa, thus resulting in fewer doses per day and better patient response and compliance.

Example 8 Effect of GRDF Formulations on Gastric Retention in Healthy Subjects and in Parkinson Patients

To determine the effect of GRDF formulations on gastric retention clinical trials were performed with various placebo GRDFs using MRI. The drug reservoir layer of the GRDF for these studies does not contain an active ingredient. Instead, the drug reservoir contains iron oxide food coloring (sicovit black e172) that can be visualized in a magnetic resonance imaging (MRI).

Results of these MRI studies showed that in healthy volunteers the GRDF formulations were retained in the stomach for 7-13 hours and for 7-24 hours in Parkinson patients.

Example 9 Carbidopa-Levodopa GRDF Formulation

-   Three additional GRDF formulations were manufactured.

mg per GRDF Levodopa 200.0 Carbidopa 50.0 KOH 6.0 Propylene glycol 94.2 Gelatin (Fish) 94.2 Eudragit L100-55 23.5 Eudragit L100 184.4 Eudragit S100 47.1 PEG 400 13.1 Tween 80 11.8 Povidone (Kollidon) 90F 13.7 Lutrol F127 (Poloxamer 407) 89.3 Total 827.3 Levodopa 300.0 Carbidopa 75.0 KOH 6.0 Propylene glycol 94.2 Gelatin (Fish) 94.2 Eudragit L100-55 23.5 Eudragit L100 83.9 Eudragit S100 47.1 PEG 400 43.5 Tween 80 14.7 Povidone (Kollidon) 90F 14.7 Lutrol F127 (Poloxamer 30.3 407) HPMCP 55 32.4 HPMCP 55 S 32.4 Total 827.0 Levodopa 300.0 Carbidopa 75.0 KOH 6.0 Propylene glycol 94.2 Gelatin (Fish) 94.2 Eudragit L100-55 23.5 Eudragit L100 93.7 Eudragit S100 47.1 PEG 400 43.4 Tween 80 14.7 Povidone (Kollidon) 90F 14.7 Lutrol F127 (Poloxamer 30.2 407) HPMCP 55 32.4 HPMCP 55 S 32.4 Total 836.8

Example 18 Carbidopa/Levodopa GRDF Immediate and Controlled Release Profiles Compared to Immediate Release Sinemet® and Controlled Release Sinemet CR® Pharmacokinetic Profiles in Healthy Subjects The Objectives of the Study

The aim of this study was to evaluate the GRDF CD/LD optimal profile, by comparing the pharmacokinetic profiles of Levodopa and Carbidopa, following oral administration of a single-dose of the three different controlled-release GRDF CD/LD formulations (Example 9) with differing ranges of release profiles, with the pharmacokinetic profiles of a single-dose of the reference formulation, Sinemet® 50/200 mg given as two 25/100 mg IR tablets. An additional objective was to monitor subjects for adverse events during the study period and to compare the safety of the test formulations with the reference formulation.

Study Design

The study was designed as a single center, randomized, single-dose, open label, four-way, four-treatment, comparative crossover study. The study included four identical dosing periods, with each period including a Carbidopa pre-treatment day and a study-drug dosing day, during which a single dose of either one of the test formulations or reference drug was administered after a light-medium breakfast. Administration was followed by pharmacokinetic blood sampling and adverse event monitoring for the next 24 hours. A single dose of GRDF CD/LD with Levodopa either 200 or 300 mg and Carbidopa either 50 or 75 mg was administered to twenty four (24) healthy male subjects aged 18-55 (inclusive) after a light meal. The GRDF CD/LD was planned for a bid dosing schedule for a total daily dose of 400-600 mg per day of Levodopa. The GRDF CD/LD was formulated to release its two active ingredients as a combination of immediate release and controlled release mechanisms to provide quick yet steady levels of Levodopa. This study tested the pharmacokinetics of the gastric retentive controlled release GRDF CD/LD after a low-medium calorie breakfast with a low protein content since protein competes with Levodopa absorption.

The Products

Test Product GRDF CD/LD Doses Administered 75/300 mg, or 50/200 mg Active Ingredient Carbidopa/Levodopa, IR + CR Dosage Form capsule

The 75/300 rug dose was tested in two formulations (a and b), the 50/200 mg dose was in one formulation.

Reference Product Sinemet ®® tablet (Carbidopa/Levodopa 25/100 mg) Dose Administered 50 mg carbidopa and 200 mg levodopa (2 tablets of 25/100 mg) Active Ingredient Carbidopa/Levodopa immediate release Dosage Form Tablet Manufacturer MERCK & CO., INC Carbidopa Pretreatment Lodosyn ® Dose Administered 50 mg (2 tablet) 3 times on Day (−1) Active Ingredient Carbidopa Dosage Form Tablet Manufacturer MERCK & CO., INC

-   The subjects were randomly assigned to a unique treatment sequence.

Study Procedures

The study drugs were swallowed whole with 240 ml of water at room temperature. Each subject was exposed to a washout period of at least 7 days between treatments.

For measurement of Carbidopa and Levodopa plasma levels, for each of the study periods, 17 serial blood samples were collected per subject. The pharmacokinetic data of Levodopa were evaluated.

Levodopa Results

The Levodopa results of 21 volunteers are shown in FIG. 13 in the Tables below:

Least-Squares Means (N = 21) GRDF GRDF GRDF CD/LD CD/LD CD/LD Sinemet ® 75/300 A 75/300 B 50/200 (2 × 100 mg) AUC 0-t 5291 5216 3732 3886 AUC 0-inf 5650 5545 3828 3945 Cmax 1240 1076 1116 1424 Tmax 2.60 2.74 2.51 1.38 MRT 0-t 5.56 6.64 4.14 2.80 MRT 0-inf 5.96 7.20 4.35 2.97 Ratios of Least Squares Means GRDF GRDF GRDF 300A/ 300B/ GRDF 300A/GRDF GRDF GRDF GRDF 300B/ 300B 200 mg 300A/Sinemet ® 200 mg Sinemet ® AUC 1.014 1.418 1.362 1.398 1.342 0-inf Cmax 1.019 1.476 1.432 1.449 1.406 Tmax 1.153 1.111 0.871 0.964 0.756 MRT 0.673 1.690 1.801 2.509 2.674 0-t MRT 0.837 1.342 1.989 1.602 2.376 0-inf AUC 0.828 1.370 2.010 1.654 2.427 0-t 90% Confidence Intervals on Least-Squares Geometric Mean Ratios GRDF GRDF GRDF 300A/ 300A/ GRDF 300B/ GRDF GRDF GRDF 300A/ GRDF 300B/ 300B 200 mg Sinemet ® 200 mg Sinemet ® AUC 0-t 90% CI Low 0.968 1.353 1.294 1.330 1.271 90% CI Hi 1.070 1.495 1.429 1.470 1.405 AUC 0-inf 90% CI Low 0.931 1.348 1.303 1.344 1.298 90% CI Hi 1.100 1.577 1.520 1.545 1.489 Cmax 90% CI Low 1.029 0.965 0.751 0.829 0.646 90% CI Hi 1.314 1.232 0.959 1.059 0.824

The results indicate that gastroretentive controlled-release delivery of levodopa yields true controlled-release behavior Both gastroretentive formulations have shown comparable bioavailability, slightly inferior to lower-doses CRDFs, and to the immediate-release formulation, as expected. The mean residence times are increased in gastroretentive controlled-release products in comparison with immediate-release formulation, two-fold and higher. The lack of proportionality of Cmax in correlation to the dose is evident, and consistent with true controlled-release behavior.

Example 11 Carbidopa-Levodopa GRDF Formulation

Two additional GRDF formulations was manufactured using the following components for the internal layer, outer layers, and an immediate release layer.

Outer (sum of Immediate Component Internal layer two films) Release Layer Total Accordion pill Carbidopa/Levodopa 50/250 mg Amount/GRDF (mg) Carbidopa 25.0 25.0 50.0 Levodopa 180.0 70.0 250.0 Eudragit S100 47.1 47.1 Eudragit L100 61.0 23.5 84.5 Eudragit L100-55 23.5 23.5 Fish Gelatin 94.2 94.2 Propylene glycol 94.2 94.2 KOH 6.0 6.0 Poloxamer 407 32.0 32.0 PEG 400 30.0 3.1 33.1 Tween 80 11.8 11.8 Povidone 90 13.7 13.7 Total 328.0 288.5 123.6 740.1 Accordion pill Carbidopa/Levodopa 50/375 mg Amount/GRDF (mg) Carbidopa 25.0 25.0 50.0 Levodopa 275.0 100.0 375.0 Eudragit S100 47.1 47.1 Eudragit L100 80.8 23.5 104.3 Eudragit L100-55 23.5 23.5 Fish Gelatin 94.2 94.2 Propylene glycol 94.2 94.2 KOH 6.0 6.0 Poloxamer 407 45.1 45.1 PEG 400 40.4 3.9 44.3 Tween 80 14.7 14.7 Povidone 90 14.7 14.7 Total 466.3 288.5 158.3 913.1

Example 12 Carbidopa-Levodopa GRDF Release Profiles

In order to illustrate the ability of the GRDF to provide both immediate release and controlled release of active ingredients, the release profile for the above two Carbidopa/Levodopa GRDF was determined. Carbidopa and Levodopa are present in total amounts of 50 and 250 or 50 and 375 mg, respectively (Example 11). Specifically, there are 25 mg Carbidopa in the immediate release layer and 25 mg in the internal layer which are provided to the patient as a controlled release. For Levodopa, 70 or 100 mg are in the immediate release layer and 180 or 275 mg in the internal layer.

Experiments were conducted in an acetate buffer (USP) pH 4.1 in a USP Apparatus 2, 50 rpm. Immediate release for both drugs occurred within 1 hour and extended release was seen for 12 hours for the 250 mg Levodopa formulation and 16 hours for the 375 mg Levodopa formulation. 

What is claimed is:
 1. A degradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the stomach and gastrointestinal tract of a patient, comprising: an internal layer comprising an active agent and a degradable polymer composition which is not instantly soluble in gastric fluid, the internal layer including a first side and an opposing second side; and at least one membrane covering the internal layer, the membrane comprising at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media, the membranes being hydratable at a rate greater than the internal layer; the membrane being directly secured to and covering both sides of the internal layer and having a predetermined length greater than 20 mm in a planar orientation, the membrane and internal layer being arranged in an accordion folded orientation sufficiently compact to be placed within a capsule dissolvable within the stomach; the membrane and internal layer developing sufficient mechanical force to unfold from the initial accordion folded orientation to a length of at least 20 mm within 30 minutes of being exposed to gastric medium, the membrane permitting passage of gastric media from the environment to the internal layer and permitting passage of the active agent from the internal layer through the membrane to the environment.
 2. The gastroretentive drug formulation of claim 1, wherein the membrane and internal layer unfold to a length of at least 20 mm within 15 minutes of being exposed to gastric fluid.
 3. The gastroretentive drug formulation of claim 1, wherein the internal layer has a mechanical strength described with Young's modulus ranging from about 0.5 to 15 Kgf/mm/² and stress of about 0.03 to about 0.6 Kgf/mm² after 1 hour in simulated gastric fluid.
 4. The gastroretentive drug formulation of claim 1, wherein the membrane includes two separate membranes, each membrane being directly joined together along an outer periphery of the membranes, the entire internal layer being located completely between the membranes, the membranes being secured to the internal layer along a portion of at least one surface of the internal layer.
 5. The gastroretentive drug formulation of claim 4, wherein the membranes are joined together with ultrasonic welding.
 6. The gastroretentive drug formulation of claim 5, wherein the membranes are joined together with the internal layer with ultrasonic welding along a region adjacent the outer periphery of the internal layer.
 7. The gastroretentive drug formulation of claim 6, wherein a central portion of the surface of the internal layer is essentially free from ultrasonic welds.
 8. The gastroretentive drug formulation of claim 4, wherein the internal layer and membranes are free of an additional adhesive member.
 9. The gastroretentive drug formulation of claim 1, wherein the multi-layered gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract comprises: an internal layer comprising an active agent and a degradable polymer composition which is not instantly soluble in gastric fluid, the internal layer including a first side and an opposing second side, a first and second membrane coveting the internal layer, the membrane including at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media, the membranes being hydratable at a rate greater than the internal layer, the first and second membrane having a width and length, greater than a width and length of the internal layer, the first and second membranes being ultrasonically welded or otherwise affixed or attached directly together about the periphery of the first and second membranes, the first membrane being attached to a first side of the internal layer, the second membrane being attached to the second side of the internal layer, the internal layer and first and second membranes having a predetermined length greater than 20 mm in a planar orientation, the membrane and internal layer being arranged in an accordion folded orientation sufficient to be placed within a capsule dissolvable within the stomach, the ultrasonic welds having sufficient mechanical strength to remain intact upon being exposed to gastric medium.
 10. The gastroretentive drug formulation of claim 11, wherein the internal layer and first and second outer layers include a central region that is substantially free of ultrasonic welds.
 11. The gastroretentive drug formulation of claim 12, wherein the ultrasonic welds between the membrane and internal layer do not penetrate entirely through the internal layer.
 12. The gastroretentive drug formulation of claim 11, wherein the ultrasonic weld pattern between the membranes and internal layer is not continuous.
 13. The gastroretentive drug formulation of claim 12, wherein the ultrasonic welds on the periphery of the membranes form a skirt region that surrounds but does not capture the internal layer.
 14. The gastroretentive drug formulation of claim 13, wherein the internal layer and first and second outer layers include a central region that is substantially free of ultrasonic welds.
 15. The gastroretentive drug formulation of claim 11, wherein the ultrasonically welded internal layer and membranes have a mechanical strength, described with Young's modulus from about 0.05 to 0.4 Kgf/mm² after 1 hour in simulated gastric fluid.
 16. The gastroretentive drug formulation of claim 15, wherein the membrane and. internal layer unfold to a length of at least 20 mm within 15 minutes of being exposed to gastric fluid.
 17. The gastroretentive drug formulation of claim 16, wherein the length of the membrane in the planar orientation is at least 30 mm.
 18. A biodegradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract, comprising: an internal layer comprising an active agent and a degradable hydrophilic polymer and a degradable enteric polymer which is substantially insoluble at pH less than 5.5, and a plasticizer, at least one membrane covering the internal layer, the membrane including at least one polymeric combination of a hydrophilic polymer and a polymer, insoluble in gastric media, and at least one plasticizer, the membrane swelling in the presence of gastric medium one of the materials in each of the internal layer and membrane being capable of being ultrasonically welded together, the membrane being directly secured to and covering both sides of the internal layer and having a predetermined length greater than 20 mm in a planar orientation, the membrane and internal layer being arranged in an accordion folded orientation sufficient to be placed within a capsule dissolvable within the stomach, the membrane permitting passage of gastric fluid from the stomach to the internal layer and permitting passage of gastric fluid and the active agent from the internal layer through the membrane to the stomach, the membrane and internal layer develop sufficient mechanical force to unfold from the accordion folded orientation to a length of at least 20 mm within 30 minutes of being exposed to gastric fluid.
 19. The gastroretentive drug formulation of claim 18, wherein the enteric polymer in the internal layer is selected from the group consisting of cellulose acetate phthalate, hypromelose phthalate, hydroxy-propyl methylcellulose acetate succinate, polyvinyl acetate phthalate and methylmethacrylate-methacrylic acid copolymers.
 20. The gastroretentive drug formulation of claim 18, wherein the polymeric combination in the outer membranes comprises gelatin.
 21. The gastroretentive drug formulation of claim 18, wherein the enteric polymer in the membrane is selected from the group consisting of one or more type of polymethacrylate USP.
 22. The gastroretentive drug formulation of claim 18, wherein the membranes comprise propylene glycol as a plasticizer.
 23. The gastroretentive drug formulation of claim 22, wherein the amount of gelatin in the membrane is an amount of between about 20% and about 45% of the total outer membrane composition.
 24. The gastroretentive drug formulation of claim 18, wherein the internal layer has a mechanical strength described with Young's modulus of from about 0.5 to about 15 Kgf/mm² find stress of from about 0.03 to about 0.6 Kgf/mm² after 1 hour in simulated gastric fluid.
 25. The gastroretentive drug formulation of claim 18, wherein the outer membrane swells at a rate faster than the inner membrane causing the accordion folded membrane and internal layer to unfold in gastric medium.
 26. The gastroretentive drug formulation, of claim 25, wherein the outer membrane that swells at a rate faster than the inner membrane thus causing the accordion folded membrane and internal layer to unfold in gastric medium is lightly affixed or attached to the said inner membrane to exert the force resulting in unfolding.
 27. The gastroretentive drug formulation of claim 1, wherein the gastroretentive drug formulation is fully degradable within 3 hours in simulated intestinal fluid.
 28. The gastroretentive drug formulation of claim 1, wherein the gastroretentive drug formulation provides gastric retention of an active agent for up to 24 hours under low or medium calorie diet to humans.
 29. The gastroretentive drug formulation of claim 1, wherein the active agent is a drug for the local treatment of the gastrointestinal tract, such as drugs for the treatment of local infections, obesity and GI pathologies.
 30. The gastroretentive drug formulation of claim 1, wherein at least one additional layer is affixed to the outer membrane on one or two sides of the gastroretentive drug formulation, and where this layer comprises a drug or a combination of drugs, together with one or more additives selected from the group consisting of water soluble polymers, a plasticizer, a solubilizing agent intended for immediate release of the drug in the stomach, a disintegrant and a glidant.
 31. The gastroretentive drug formulation of claim 29, wherein the active agent comprises a drug selected from the group consisting of levodopa and carbidopa.
 32. The gastroretentive drug formulation of claim 31, where the formulation contains 250 mg of levodopa and 50 mg of carbidopa.
 33. The gastroretentive drug formulation of claim 32, wherein 70 mg of the levodopa and 25 mg carbidopa are formulated as an immediate release component, whereas the rest of the carbidopa and the levodopa are released in a controlled manner over 8-10 hours.
 34. The gastroretentive drug formulation of claim 31, where the formulation contains 375 mg of levodopa and 50 mg of carbidopa.
 35. The gastroretentive drug formulation of claim 34, wherein 100 mg of the levodopa and 25 mg carbidopa are formulated as ail immediate release component, and wherein the rest of the carbidopa and the levodopa are released in a controlled manner over 8-10 hours.
 36. The gastroretentive drug formulation of claim 1, wherein the inner compartment comprises one layer intended as backbone to increase the mechanical strength of the formulation, and to this layer are attached on one or two sides additional layer or layers containing the active ingredient or ingredients and an inactive ingredient and intended for the controlled release of the drug and wherein these layers are covered by and contained between two layers of outer membrane as described previously in these claims.
 37. A biodegradable, multi-layered gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract, comprising: an internal layer comprising an active agent and a degradable hydrophilic polymer which is not instantly soluble in gastric fluid and a degradable enteric polymer which is substantially insoluble at pH less than 5.5, and a plasticizer, the internal layer including a first side and an opposing second side, a first and second membrane covering the internal layer, the membranes including at least one polymeric combination of a hydratable swelling polymer and an enteric polymer, and at least one plasticizer, the membrane swelling in the presence of gastric fluid, one of the materials in each of the internal layer and membranes being capable of being ultrasonically welded together, the membranes being directly secured to and covering both sides of the internal, layer and having a predetermined length, greater than 20 mm in a planar orientation, the membranes and internal layer being arranged in an accordion folded orientation sufficient to be placed within a capsule dissolvable within the stomach, the membranes and internal layer developing sufficient mechanical force to unfold from the accordion folded orientation to a length of at least 20 mm within 30 minutes of being exposed to gastric fluid, the first and second membranes having a width and length greater than a width and length of the internal layer, the first and second membranes being ultrasonically welded directly together about the periphery of the first and second membranes, the first membrane being ultrasonically welded to a first side of the internal layer, the second membrane being ultrasonically welded to the second side of the internal layer, the membrane permitting passage of gastric fluid from the stomach to the internal layer and permitting passage of gastric fluid and the active agent from the internal layer through the membrane to the stomach, the internal layer and first and second membranes having a predetermined length greater than 20 mm in a planar orientation, the membrane and internal layer being arranged in an accordion folded orientation sufficient to be placed within a capsule dissolvable within the stomach, the ultrasonic welds having sufficient mechanical strength to remain intact upon being exposed to gastric medium.
 38. A gastroretentive drug formulation for the sustained release of an active agent in the gastrointestinal tract comprising: i.) an internal layer or compartment comprising an active agent, and one or more pharmaceutical excipients, of which at least one is a polymer; i.i.) two membranes forming together an envelope around the inner membrane, each membrane comprising at least one polymeric combination of an hydrophilic polymer and a polymer, insoluble in gastric media, and at least one plasticizer; and iii.) optionally an additional layer covering each outer membrane comprising a powder or a film that prevents adherence of the outer membrane onto itself when folded inside the capsule.
 39. The gastroretentive drug formulation of claim 38 further including one or two layers comprising the active agent and a soluble polymer that provides for the immediate release of the active agent and being attached to the outside of one outer membrane or two outer membranes or part of the outer membrane.
 40. The gastroretentive drug formulation of claim 38 wherein, the internal layer and membranes effectively unfold from an accordion folded orientation and are stable in acidic pH for up to 24 hours and completely biodegrade after 3 hours in simulated intestinal fluid.
 41. The gastroretentive drug formulation of claim 39, wherein,, the polymer in the internal layer is selected from the group consisting of a degradable hydrophilic polymer which is not instantly soluble in gastric fluid and a degradable enteric polymer which is substantially insoluble at pH less than 5.5.
 42. The gastroretentive drug formulation of claim 41, wherein the enteric polymer in the internal layer is polymethacrylate copolymer.
 43. The gastroretentive drug formulation of claim 41, wherein the enteric polymer is at least one of cellulose acetate phthalate, hypromelose phthalate, hydroxypropyl methylcellulose acetate succinate, polyvinyl acetate phthalate or cellulose acetate trimellitate.
 44. The gastroretentive drug formulation of claim 38, wherein the active agent and the polymer are uniformly distributed in the internal layer.
 45. The gastroretentive drug formulation of claim 38, wherein the polymeric combination in the outer membranes comprises gelatin and cellulose acetate succinate.
 46. The gastroretentive drug formulation of claim 38, wherein the enteric polymer in the membranes is polymethacrylate copolymer USP type A.
 47. The gastroretentive drug formulation of claim 38, wherein the enteric polymer in the membranes is polymethacrylate copolymer USP type C.
 48. The gastroretentive drug formulation of claim 38, wherein, the plasticizer in the outer membranes is propylene glycol.
 49. The gastroretentive drug formulation of claim 38, wherein the internal layer or compartment, the membranes and the optional additional layers or the immediate release layers are joined by applying ultrasonic welding.
 50. The gastroretentive drug formulation of claim 38, wherein, the internal layer provides at least 50% of the mechanical strength of the welded internal layer and membranes when wetted with gastric medium.
 51. The gastroretentive drug formulation of claim 38, wherein the GRDF reaches its eventual maximum strength within less than two hours in simulated gastric fluid.
 52. The gastroretentive drug formulation of claim 38, wherein, the internal layer has a planar-accordion geometry that unfolds to at least 50% of its original length within 30 minutes in simulated gastric fluid.
 53. The gastroretentive drug formulation of claim 38, wherein the internal layer and membranes are fully degradable within 3 hours in simulated intestinal fluid.
 54. The gastroretentive drug formulation of claim 38, wherein the GRDF comprises an internal layer that provides gastric retention for up to 24 hours under low or medium calorie diet.
 55. The gastroretentive drug formulation of claim 38 is designed for oral administration and are compacted or folded into a standard size capsule which is easily swallowed.
 56. The gastroretentive drug formulation of claim 38, wherein the active ingredient or ingredients are incorporated in the internal layer as one or more of solid solutions, powders, grains, spheres, particles, microparticles, nanoparticles, multiparticulates, or microcapsules.
 57. The gastroretentive drug formulation of claim 38, wherein the active agent has a narrow window of absorption in the gastrointestinal tract, the active agent being one or more of a therapeutic nucleic acid sequence, a therapeutic protein or peptide, a peptidomimetic drug, a nucleoside analogue, an aminoacid analogue, an antibiotic, a therapeutic ion, a vitamin, a bronchodilator, an anti-gout agent, an anti-hypertensive agent, a diuretic agent, an anti-hyperlipidemic agent, an ACE inhibitor, a CNS active agent, an anti-tumor agent, an histamine (H2) blocker, a bismuth salt or a synthetic prostaglandin.
 58. The gastroretentive drug formulation of claim 57, wherein the active agent is levodopa.
 59. The gastroretentive drug formulation of claim 57, wherein the active agent is a drug for the local treatment in the gastrointestinal tract, or for the treatment of local infections, gastrointestinal diseases and symptoms, metabolic disorders, local cancers or cancer-related diseases. 